This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, May 31. All times are given as local St. Louis time (Central Daylight Time). For definitions of terminology used in the night sky update, click the highlighted text.

Information updated weekly or as needed.

Join us for our next star party, Friday, June 3, 2016 held in association with the St. Louis Astronomical Society. For details, see the information at the bottom of this page.

The Sun and the Moon

Sunrise is at 5:39 a.m. on Tuesday, May 31 and sunset is at 8:19 p.m. providing us with roughly 14.5 hours of daylight. Even after sunset, the light from the Sun will still dimly illuminate our sky for nearly two hours. This period of time is called twilight, which ends around 10:14 p.m. this week. For those with a sun dial, solar transit or local noon occurs around 12:59 p.m. this week.

Day

Sunrise

Sunset

31 May

5:39 a.m.

8:19 p.m.

01 Jun

5:38 a.m.

8:20 p.m.

02 Jun

5:38 a.m.

8:21 p.m.

03 Jun

5:37 a.m.

8:21 p.m.

04 Jun

5:37 a.m.

8:22 p.m.

05 Jun

5:37 a.m.

8:23 p.m.

06 Jun

5:37 a.m.

8:23 p.m.

07 Jun

5:36 a.m.

8:24 p.m.

08 Jun

5:36 a.m.

8:24 p.m.

Moonrise for Tuesday, May 31 occurs at 2:40 a.m. and moonset will occur at 3:15 p.m. On May 31 the moon will be exhibiting a waning crescent phase with about 26% disk coverage. New moon occurs on Saturday, June 4.

International Space Station (ISS) Observing

This week visible passes of ISS from St. Louis will occur during early morning and late evening hours. The best passes this week occur on June 6 and 8. Use the table below for information regarding this pass and others this week.

The Red planet is currently found in Ophiuchus rising before the Sun and can be easily seen by 9:30 p.m. in the southeastern sky. Mars sets by 4:59 a.m.

Jupiter

Jupiter now rises before the Sun sets. To see Jupiter you will have to look south at about 8:50 p.m. Jupiter sets at 1:54 a.m. Each week Jupiter will set approximately 30 minutes earlier than it did the week before.

Saturn

The ringed planet is rising before midnight and can be seen in the southeast shortly after twilight ends. Saturn rises at 8:22 p.m. and can be seen low in the southeast around 10:00 p.m. Saturn will reach opposition on June 3.

Deep Sky Object of the Week

A few years ago the night sky update included a section that highlighted one constellation a month and a few objects of interest inside of it. Unfortunately of the 88 constellations there are only about 60 we can see in St. Louis and of these there are only so many that have enough objects to reference that would interest both beginners and advanced observers. In 2015 we changed things a bit for this section and instead of highlighting one constellation for each month we highlighted one Messier object a week using the Astronomical League’s Binocular Messier program as our guide. We will continue this into 2016 but instead of using the Astronomical League’s binocular Messier program we will use their Binocular Deep Sky Program.

The Astronomical League is an amateur astronomy society that is composed of over 240 local amateur astronomy societies across the United States and includes members at large and other supporting members. Their goal is to promote the science of astronomy through education, incentive and communication.

One of the many ways the Astronomical League has assisted amateur astronomers around the world is by creating various observing programs that highlight different aspects of astronomy and how an amateur astronomer can observe the sky and learn more about astronomy in doing so. Some of these programs are introductory and are targeted at those beginning to learn about observational astronomy and some are extremely advanced, require specialized equipment and require a large amount of time to complete. These observing programs cover most any type of object or way to observe the sky so everyone should be able to find one that matches their interests and abilities. It is important to note that these programs are not part of any class or lecture series but are rather lists of objects that highlight types of objects or observing methods relevant to astronomy. Taking part in these programs is done under one’s own choice. To officially complete each program you do have to be a member of the Astronomical League but you do not have to join to use them as observing guides or education tools. I would urge anyone interested in astronomy to look at these programs as they will help organize observing sessions and will help refine observing skills you already have. You can find out more information about the Astronomical League’s observing programs here https://www.astroleague.org/observing.html

The observing program we will use to help guide us through the 2016 observing year is the Binocular Deep Sky Program. This is a program that will appeal to both beginning and advance observers. Too often it is thought that you need to have a telescope for astronomical observations. Telescopes make great observing tools and yes they can show you more than binoculars but they do have their limitations. Cost, size, weight and complexity will often be a surprise to people when they first learn about telescopes. These factors can keep people from using telescopes they own or from buying one at all. The best advice to follow is a good observing tool is one you will use.

The binocular deep sky program is an introduction to deep sky objects beyond the Messier catalog. It will introduced viewers to the New General Catalog (NGC) and some of the lesser known deep sky catalogs such as the Stock, Collinder and Melotte. Each week we will highlight a deep sky object that is part of the Astronomical League’s binocular deep sky program. This program is tougher than Messier binocular program as the objects are not always as obvious and they will require larger binoculars than the Messier program. 50mm binoculars are recommended but many of the targets can be seen through smaller aperture instruments. I would urge each observer to fulfill the requirements of the program even if you do not intend to join the League for completion. The requirements involve logging observing data that can help refine observing skills that will be useful later down the road. If you have an interest in astronomy and learning more about observational astronomy I would also recommend checking out one of the two excellent astronomy societies near St. Louis. Both are members of the Astronomical League and both do numerous public observing nights around town. These clubs are the

If you do not live in the St. Louis, Missouri area chances are you have similar astronomical societies where you live.

The deep sky object for the week of May 3 is the open star cluster Melotte 111 (Mel 111). This open cluster of roughly 40 stars is estimated to be 288 light years away making it one of the closest star clusters to our solar system. At this distance these stars shine with an apparent magnitude of 1.8 making it visible to the unaided eye. At 400 million years old this cluster is quite young. When these stars first started to shine some of the earliest land plants were starting to appear on the Earth.

Since Mel 111 is so bright it is hard to imagine why it was not included on Messier’s or Herschel’s lists of deep sky objects. The simple reason why is Mel 111 was not proven to be a star cluster until 1938 when R.J. Trumpler was able to prove the 37 stars were true cluster members.

Located in the constellation Coma Berenices, Mell 111 can be found by starting with the Big Dipper in Ursa Major. You can find the Big Dipper in the due north around 10:00 p.m. If you find the handle of the Big Dipper and begin to scan to the south you will find the bright star Cor Caroli in Canes Venatici. From here Coma Berenice will be another ten degrees south of this star. Mel 111 can be found just south of the bright star Gamma Comae Berenices. To the unaided eye it will appear as a faint smudge of light in the sky and through binoculars you will find a bright scattering of stars that will fill most of your field of view. Use the maps below to find Mel 111 in Coma Berenices.

The deep sky object for the week of May 10 is the open star cluster IC 4665. IC 4665 is part of the Index Catalog which is an update to the New General Catalog (NGC). The Index Catalog was published in two parts, the first in 1895 and the second in 1908. Together the IC I and IC II catalogs document the discovery of galaxies, star clusters and nebulae between the years 1888 and 1907 which together contain 5,386 objects.

This week’s target IC 4665 is an open star cluster that is comprised of approximately 30 stars that are estimated to be 36 million years old. These stars first started to shine around the same time a major extinction event occurred on the Earth known as the Eocene-Oligocene extinction. This extinction event primarily affected marine life and was thought to be caused by large meteorite impacts. One of these was the Popigai impact in Siberia and the other was the impact that created Chesapeake Bay impact crater off the east coast of Virginia.

At a distance of 1,400 light years IC 4665 shines with an apparent magnitude of 4.2 making it an easy target even in light polluted skies. The Trumpler classification for IC 4665 is III, 2, p which means it is a detached star cluster with no central concentration, it has a moderate range of stellar magnitudes and it is a poor cluster with less than 50 members.

To find IC 4665 you will have to locate the constellation Ophiuchus the Serpent Bearer. This constellation can be found by first looking for the asterism known as the Summer Triangle. This can be found by looking east around 11:00 p.m. The Summer Triangle is made up of the bright stars Vega, Deneb and Altair which are found in the constellations Lyra, Cygnus and Aquila respectively. Your next step is to find the planet Mars. Right now Mars can be found in the constellations Scorpius which will be seen in the south around 11:00 p.m. Mars will be unmistakable as it is the brightest object you can currently see in the southern skies after 10:00 p.m. Once you can find both the star Vega and the planet Mars your next step will be to identify the bright star that is seen halfway between them called Rasalhague. This is the brightest star in Ophiuchus and is near the location of IC 4665. Once you can find Rasalhague or what some maps may label Alpha Ophiuchi you will want to grab your binoculars and scan to the southeast to find the next bright star Cebalrai (Beta Ophiuchi). About one degree to the north of this star you will find a large scattering of bright stars which is IC 4665. For more assistance use the maps below.

The deep sky object for the week of May 17 is the open star cluster NGC 6520. This young open star cluster contains about 60 members which formed roughly 54 million years ago. At a distance of 5,400 light years this star cluster is possibly located in the next arm in of the Milky Way Galaxy. At this distance NGC 6520 will shine with an apparent magnitude of 7.6 making it a doable target for city observers but it will be a challenge. NGC 5260 has a Trumpler classification of I, 2, m which means it is well detached from background stars with a strong central concentration, its stars have a moderate range of stellar magnitudes and it has a moderate population as it contains between 50 and 100 stars.

NGC 6520 is located in the constellation Sagittarius which can be found in the south around 1:00 a.m. To find Sagittarius it is best to start by locating the constellation Scorpius. If you look south around 1:00 a.m. you will find a bright fishhook shape of stars which is Scorpius. Looking to the east of the fishhook you will see what looks like a teapot shape of stars. This is the famous Teapot asterism which is the pattern you look for to identify Sagittarius. Once you find this shape you need to identify the stars Delta and Gamma Sagittarii. NGC 6520 can be found about two degrees north of Gamma Sagittarii. Through binoculars it will look like a small fuzzy patch of light. Use the links below for help in locating NGC 6520.

The deep sky object for the week of May 24 is the open star cluster NGC 6633. Located in Ophiuchus about 1000 light years away, NGC 6633 shines with an apparent magnitude of 4.6. At this magnitude NGC 6633 will be an easy target for those observing from a light polluted location. It has 30 known members which are thought to be about 660 million years old. Around the time these stars began to shine Earth was nearing the end of an extreme deep freeze. The end of this deep freeze marks the beginning of the Cambrian period in which Earth saw an extreme burst of evolutionary changes of life. Some of the earliest animals evolved around this time.

Sky Atlas gives NGC 6633 a Trumpler classification of III, 2 m which means it is detached from background stars but has no central concentration, it has a moderate range in stellar magnitudes and it has between 50 to 100 stars. This last part of the Trumpler classification is confusing as Sky Atlas also says NGC 6633 only has 30 member stars.

To find NGC 6633 you will have to locate the constellation Ophiuchus. This constellation can be found by first looking for the asterism known as the Summer Triangle. The Summer Triangle can be found by looking east around 11:00 p.m. It is made up of the bright stars Vega, Deneb and Altair which are found in the constellations Lyra, Cygnus and Aquila respectively. Once here draw a line extending from Deneb to Vega and continue until you find a bowtie shape of stars. The bowtie shape is located west of the Summer Triangle about the same distance that is seen between the stars Deneb and Vega. The bowtie shape is the constellation Hercules which lies just north of Ophiuchus. South of the bowtie shape is the brightest star in Ophiuchus called Rasalhague. Once you can find Rasalhague or what some maps may label Alpha Ophiuchi you will want to grab your binoculars and scan to the southeast to find the next bright star Cebalrai (Beta Ophiuchi). From here scan east until you find a large bright scattering of stars. This is NGC 6633 which is about 10 degrees east of Cebalrai. Use the maps below for assistance.

The deep sky object for the week of May 31 is the open star cluster IC 4756. This young group of stars can be found in the constellation Serpens at a distance of 1,300 light years. At this distance it shines with an apparent magnitude of 4.6 making it an easy target for binocular observers in light polluted areas. IC 4756 contains about 80 stars that are estimated to have formed 580 million years ago. It has a Trumpler classification of III, 2, m which means it is well detached from background stars containing no central concentration, it has a moderate range of stellar magnitudes and it has a moderately dense population having between 50 and 100 stellar members.

To find IC 4756 use the same methods described for last week’s object. Again look for the asterism known as the Summer Triangle. The Summer Triangle can be found by looking east around 11:00 p.m. It is made up of the bright stars Vega, Deneb and Altair which are found in the constellations Lyra, Cygnus and Aquila respectively. Once here draw a line extending from Deneb to Vega and continue until you find a bowtie shape of stars. The bowtie shape is located west of the Summer Triangle about the same distance that is seen between the stars Deneb and Vega. The bowtie shape is the constellation Hercules which lies just north of Ophiuchus. South of the bowtie shape is the brightest star in Ophiuchus called Rasalhague. Once you can find Rasalhague or what some maps may label Alpha Ophiuchi you will want to grab your binoculars and scan to the southeast to find the next bright star Cebalrai (Beta Ophiuchi). From here scan east until you find a large bright scattering of stars. This is NGC 6633 which is about 10 degrees east of Cebalrai. Once you have found NGC 6633 scan another four degrees further and you will find IC 4756. Together NGC 6633 and IC 4756 are known as the Tweedledee and Tweedledum clusters. Use the maps below for assistance.

Our next Star Party will be held on Friday, June 3, 2016, from dusk until 10 p.m.

As part of the Saint Louis Science Center’s First Fridays, weather permitting, the St. Louis Astronomical Society and the Science Center will set up a number of telescopes outdoors and be on-hand to answer your questions. Telescope viewing begins once it is dark. Regardless of the weather on June 3, join us indoors in our planetarium theater for “The Sky Tonight”. Showtime is at 7 p.m.

This free, indoor star program will introduce you to the current night sky, the planets, and the seasonal constellations. Doors open 15 minutes before show time. Shows begins at 7 p.m. Sorry, no late admissions due to safety issues in the darkened theater.

The St. Louis Astronomical Society helps host the monthly Star Parties at the Saint Louis Science Center which are held on the first Friday of each month. Our Monthly Star Parties are open to the public and free of charge.